Dawn of the Planet of the Apes) presents a pretty good illustration of the forces that drive groups into violent conflict, or provide opportunities for diplomacy. As the story begins, we find a rapidly-evolving colony of apes living in the woods, while a group of humans, perhaps all that is left of humanity (most people having been wiped out by a virus and the mass chaos caused by the virus) are struggling to survive in what's left of San Francisco. An exploring party makes contact with the apes, and both sides have to decide whether to go to war against the other, or find a way to co-exist peacefully.
On each side, there is an advocate for peace, and a counter-advocate for war. The apes' leader, Caesar, still has kindly feelings toward humans, and thinks they might be able to establish trust and respect each other's boundaries, while his rival Koba wants to keep humans away or destroy them. The two points of view on the human side are represented by Malcolm, who asks for a chance to negotiate with the apes to allow the human city to re-build, and Dreyfus, who is skeptical of this diplomatic mission, and makes preparations to fight.
What I liked about this set-up is that there is a logic to each of these four points of view. The dreamers on each side who hold out hopes for peace are correct in pointing out the awful toll that war would take. They recognize the risks, but only ask for a chance to test whether a means can be found for both groups to achieve their goals without threatening the other's. On the other hand, those who advocate for war are correct in suggesting that the other side cannot be fully trusted, and that peaceful coexistence might never be possible.
The movie also demonstrates the powerful roles that fear, distrust, selfishness and bias all play in leading both sides toward violent conflict. Peace is difficult to achieve, and fragile to maintain. It requires individuals to get to know and understand individuals on the other side. It requires trust, which can easily be broken. War seems natural for those not ready to shed their prejudices and fears.
An important lesson for conflict resolution is well illustrated in this film. That is that you generally can't use logic and reason to persuade people to avoid taking a confrontational approach. The hawks will not be persuaded by logic, and their arguments are just as strong as those of the doves. Instead you have to appeal to deeper emotional needs, such as self-preservation or brotherhood, in order to avoid destructive conflict.
(For those who prefer historical drama to science fiction, an even better movie with similar themes is Ridley Scott's Kingdom of Heaven, illustrating the forces that drove both sides to war leading up to the siege of Jerusalem in 1187.)